When a medical treatment is conducted by liquid transfusion or blood transfusion in medical facilities, a three-way stopcock is used for carrying out mixture injection of different types of medical fluid and for taking a fluid flowing through a fluid flow passage. FIG. 9 shows an overall perspective view of a conventional three-way stopcock, in which the conventional three-way stopcock is configured with: a body 1 provided with branch pipes that are connected to three branch openings and in which a fluid can flow; and a flow passage switching portion 5. The conventional three-way stopcock is configured in a manner that a rotational operation of a handle 7 configured integrally with the flow passage switching portion 5 allows the selection of a combination of a branch pipe into which a medical fluid flows and a branch pipe communicating with the branch pipe so that the medical fluid flows out of there.
Out of the three branch pipes in the conventional three-way stopcock, a first branch pipe 31 and a second branch pipe 32 are arranged so as to assume a straight-line flow passage form when they communicate with each other. This flow passage is designated as a main line. In addition, a branch pipe that is arranged perpendicularly to the main line is a third branch pipe 33, through which mixture injection of medical fluids is carried out and a fluid is taken.
FIG. 10 is a transverse sectional view of the conventional three-way stopcock. As shown in FIG. 10, the body 1 is provided with the three branch openings 21, 22 and 23 so as to allow the selectable combination of the first branch pipe 31, the second branch pipe 32 and the third branch pipe 33.
FIG. 11 schematically shows the direction of a flow passage in the flow passage switching portion of the conventional three-way stopcock. As shown in FIG. 11, the flow passage switching portion 5 is provided with three flow passage openings 61, 62 and 63. In addition, a fluid flow passage 8 provided in the flow passage switching portion 5 is configured with a flow passage through which the first flow passage opening 61 and the second flow passage opening 62 communicate with each other in a straight line and a flow passage that is arranged so as to branch perpendicularly from the center of this flow passage so as to communicate with the third flow passage opening 63. In other words, the fluid flow passage 8 is configured in the shape of a T.
The third branch pipe 33, however, might be opened to the outside during the mixture injection, resulting in the possibility that bacteria get into there. That is to say, as the third branch pipe 33 has a hollow and long-size pipe structure and it is difficult to disinfect the long-size bore of the pipe, there is the risk that the bore in the third branch pipe 33 becomes a breeding ground for bacteria.
Furthermore, since the flow passage switching portion 5 is configured, as shown in FIG. 10, in the shape of a T with a portion branching partway, there is the risk that the flow of the main line does not affect the portion X in the flow passage that communicates with the third flow passage opening 63, resulting in the generation of a stagnated portion. Due to the presence of the stagnated portion, a medical fluid to be given might remain there, which causes a problem that it becomes difficult to administer the medical fluid precisely.
Meanwhile, in the recent medical scenes, as an insertion member for mixture injection equipment such as an injection needle for use in mixture injection, a specially designed blunt needle is used instead of a sharp metal needle.
Correspondingly, various three-way stopcocks have been developed, as disclosed in JP 11(1999)-342209 A, in which a septum of an elastic member having a slit through which a blunt needle can be punctured is provided at a position corresponding to the third branch pipe for the purpose of eliminating the stagnated portion in the third branch pipe 33. The three-way stopcock disclosed in JP 11(1999)-342209 A is a medical stopcock having a feature in which an arcuate groove-like switching passage is formed along the circumferential surface at the switching portion of the flow passage. In this three-way stopcock, the septum of an elastic member having the slit is disposed at the position corresponding to the third branch pipe 33, so that the branch pipe is isolated from the outside so as to secure a closed system and at the same time the length of the flow passage can be shortened relative to the conventional one. In addition, by forming the arcuate groove-like switching passage along the circumferential surface at the switching portion of the flow passage, a flow of the fluid is generated also at the portion conventionally acting as the stagnated portion, so as to eliminate the stagnated portion.
These three-way stopcocks, however, have a drawback in that a closing of all of the flow passages cannot be made by adopting a method in which an angular position of the fluid flow passage is shifted slightly, which is a normal method in the conventional three-way stopcocks. That is to say, there is a problem in that it is not possible to close all of the flow passages by rotating the flow passage switching portion 5 from the state of FIG. 10 to a state corresponding to an intermediate angular position within an angle made by the position of the third branch pipe 33 and the position of the first branch pipe 31 or the second branch pipe 32 (45° or 315°) as in the conventional methods.
For example, in the three-way stopcock disclosed in JP 11(1999)-342209 A, when all of the flow passages are closed, the fluid switching portion 5 should be rotated by about 135° to 225°. This results from the fact that, while the flow passage switching portion 5 in the conventional three-way stopcocks has three openings, this flow passage switching portion 5 has an arcuate groove form along the circumferential surface, which means the opening portion is open to a large degree. In the practical medical scenes, in particular, complicated operations should be done securely in a short time, and therefore the three-way stopcock having such a configuration has the possibility of operating errors occurring during the use thereof.